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' t � > _. The Stack at Legacy Point Drainage Report 711 Church Avenue College Station, Texas February 2012 Prepared for: 5G Studio Collaborative 800 Jackson Street, Suite 500 Dallas, TX 75202 Prepared by: Kimley-Horn and Associates, Inc. 2800 South Texas Avenue Suite 201 Bryan, Texas 77802 Texas Registered Engineering Firm F-928 ❑Kimley-Horn ❑ and Associates, Inc. Executive Summary Report Contact Information Owner Culpeper Family L.P. 1700 George Bush Avenue East, College Station, Texas 77840 (979)696-1444 Contact: Jack Culpeper Identification Engineer Kimley-Horn and Associates, Inc. Suite 240 2800 South Texas Avenue, Suite 201 Bryan, Texas 77802 (979)775-9595 Contact: Chris Harris, P.E. The Stack at Legacy Point site is located at 711 Church Avenue. The property is a 3.05acre tract known as Lot 1-R of The Ramparts subdivision. Location The subject tract is currently an undeveloped parcel located north of Church Avenue and behind an existing shopping center. This tract is located within the City of College Station. No portion of the subject property is located within the Special Flood Hazard Areas indicated on the FEMA Flood Insurance Rate Map. Panel Map number 48041 C0144 C is included in Appendix A for reference. Current Conditions The subject tract is currently an undeveloped parcel and has been used as a construction laydown and staging area. The tract is generally barren with some low grass vegetation. The property currently discharges in three directions. The northern portion of the property sheet flows north to an adjacent access drive on the adjoining property. A portion of the northern part of the site also sheet flows onto the eastern adjoining property into an existing access drive which then discharges north. The majority of the property currently discharges south towards Church Avenue and an existing retail building. This flow combines with off site flows from Church Avenue and from the surrounding retail developments south of the southern property line. These flows appear to be intercepted in a private storm sewer inlet located off of Church Avenue north of the existing Taco Bell site. A junction point (Junction 1) has been incorporated into the modeling to represent the flows discharging from the site prior to the combination of off site flows. Hydrologic Characteristics The subject site has been designed with a underground detention facility due to its location and the available outfall conditions. One detention facility has been provided to attenuate post -development flows discharging to the south. The area of the tract discharging north and east will be attenuated to match existing flows by limiting the proposed drainage areas. The tract is classified as "Urban Development" in the Brazos County Soils Report. The on -site soils exhibit low infiltration rates and were classified as Hydrologic Class D soils per the Natural Resources Conservation Service's Curve Number method. Considering these criteria the existing groundcover conditions were assigned a Curve Number of 79 with 0 percent impervious cover. The fully developed property will consist of an urban style dormitory building project. We have estimated the total impervious cover for the tract at 95%. The grades on the site will range from 0.5% to 5%. All three outfall peak discharges will be matched or reduced for the 2, 10, 25, and 100 year recurrence storm events per the hydrologic model developed with HEC-HMS 3.5. The on -site detention facility was designed using HEC-HMS 3.5 software along with the NRCS curve number method with criteria consistent with the City of College Station Unified Stormwater Design Guidelines Dated February 2009. The hydrologic analysis for the subject site, using HEC-HMS 3.5, can be found in Appendix B_ The drainage areas used in the HEC-HMS 3.5 analysis can be seen on the plan sheets entitled Existing Conditions Drainage Area Map and Proposed Drainage Area Map located in Appendix B of the report. Hydraulic Criteria As designed, the runoff to the north and east will maintain its current flow pattern of sheet flow off of the property. The portion that discharges to the southern property will be captured in an underground storm system and piped to the existing curb inlet north of Taco Bell. This inlet is the current outfall point for this drainage. On site drainage will be captured via inlets and building roof drains and piped into an underground detention storage tank. This tank then discharges into a storm system with a control structure built into a junction box. The control structure has both an orifice and a weir to stage the various release rates per the storm events. This junction structure will also serve as an emergency over flow via a grate top. The detention pond is currently sized to hold 0.48 acre-feet of volume. The required storage volume for the pond in the 100 year event is 0.41 acre-feet (0.37 ac-ft storage plus 10% sedimentation). The max water surface elevation in the pond with an assumed plugged orifice is 336.92. The proposed pond outfall structure, designed to match or reduce the peak discharges for the 2, 10, 25, and 100 year storm events, is an orifice, and a sharp -crested weir constructed in a 4' junction box. The orifice is 8" wide and 6" tall with an invert elevation at the base of the junction box. The weir is designed to be 4'-0" wide with atop elevation of 335.80. The top of the junction box will have a grate top to allow any emergency overflow to discharge from the structure. The grate is set at an elevation of 338.62. However, a model run with the bottom orifice plugged yields a maximum water surface elevation of 336.96, 1.66' below the emergency overflow. The drainage system is designed to convey, collect, and release runoff from the site at flows that do not exceed existing discharges, based on each of the design storms, entering the respective outfall point. Coordination and Permitting No coordination of stormwater with entities outside the City of College Station will be required. Included by Reference The following documents are included by reference: • drainage report dated February 14, 2012. • The Stack at Legacy Point, Civil Engineering Plans by Kimley-Horn and Associates, Inc. "This report for the drainage design of The Stack at Legacy Point was prepared under my supervision in accordance with provisions of the Bryan/College Station Unified Drainage Design Guidelines for the owners of the property. All licenses and permits required by any and all state and federal regulatory agencies for the proposed drainage improvements have been issued. " T/ e• .zoiZ ---- Licensed rrofessional Engineer State of Texas No. 94'86"? J. CHRIS HA a: 94859 Appendix A FEMA FIRM Map No. 48041CO144 C Appendix B HEC-HMS 3.5 HNdrologic AnalN sis e SOP ' .� PO �' 1 • 5a t 4J iQ �x �y ............. F I C. I. I I . I. s■ w. I m�N I. I. I ■ i I I . I � a --111 *I I! ! ............ J., i • .FfiiFF�L "•:l: iF� .f�{. �.�.9f�.'!�f'�.#-i'�. ii..FF'..FFF.'F.. _ ...y iifS \] ti s� :a �a m� o m ox 3 €n 8 ^� 03 8 g o m o n a m m > n n a n A'.. •�^• 0 0 0 0 0 0 ova >AC ,d, z I Nz------ v) N T=m q 3 ` 3 T;-2 o g= D De Da MA �flr =og Z 1� rn zv £ a Oz o aH 7 O gw 4 g P z A. a Al gA $ i J O C n D r r ODMGNIM2�DY 9 THE STACK a ��� Kimley-Horn 2 9 a RAMPARTS LOT 1-R PROPOSED DRAINAGE AREA MAP SCALEo /�1 and Associates, Inc. co m JCR $ ® \TERAS 11.11111 EJSNEEaNCDneM ! szeCITY OF COLLEGE STATION, TEXASNDO savor RxnE AYNlLE scl lE 3m 'Ry"ne0z c XONE'. 9I9]595 ND. REVI$IQN$ DAiE BY MJM WWWMIN LE V-rvOT x.COu Pre -Development Conditions Drainage Area Basin Area (acres) Percent Impervious Curve Number Time of Conc. (min) Lag Time (min) EXl 2.04 0 79 10.0 10.0 EX2 0.32 0 79 10.0 10.0 EX3 0.57 0 79 10.0 10.0 OS1 2.68 90 79 10.0 10.0 OS2 1.62 100 79 10.0 10.0 Total Acreage I7.23 Post -Development Conditions Drainage Area Basin Area (acres) Percent Impervious Curve Number Time of Conc. (min) Lag Time (min) Al 0.45 95 79 10.0 10.0 A2 1.4 95 79 10.0 10.0 A3 0.02 95 79 10.0 10.0 A4 0.17 95 79 10.0 10.0 A5 0.03 95 79 10.0 10.0 A6 0.1 95 79 10.0 10.0 A7 0.11 95 79 10.0 10.0 A8 0.12 95 79 10.0 10.0 B1 0.08 95 79 10.0 10.0 B2 0.21 95 79 10.0 10.0 Cl 0.25 95 79 10.0 10.0 OSl 2.68 90 79 10.0 10.0 OS2 1.62 1 100 1 79 1 10.0 1 10.0 Total Acreage 7.24 2 Year Recurrence Interval Event Pre -Development Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff (cfs) EXl 2.04 0 79 12: 12 4.49 Junction 1 - - 12:12 4.49 OS1 2.68 95 79 12:11 9.81 CS2 1.62 100 79 12:11 6.14 Outfalll 12:11 20.39 EX2 0.32 0 79 12:12 0.7 Outfall2 - 12:12 0.7 EX3 0.57 0 79 12:12 1.25 Outfall3 - - - 12:12 1.25 Post -Development Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff (cfs) Al 0.45 95 79 12:11 1.69 A2 1.40 95 79 12:11 6.30 A3 0.02 95 79 12:11 0.08 A4 0.17 95 79 12:11 0.64 AS 0.03 95 79 12:11 0.11 A6 0.10 95 79 12:11 0.38 A7 0.11 95 79 12:11 0.41 A8 0.10 95 79 12:11 0.38 A9 0.02 95 79 12:11 0.08 OSS 2.68 95 79 12:11 9.81 OS2 1.62 95 79 12:11 6.14 Junction la - 12:15 3.55 Junction 1 - 12:13 4.48 Outfall1 - 95 79 12:11 20.38 BS 0.08 1 95 79 12:11 0.30 B2 0.20 95 79 12:11 0.19 Outfall2 - - - 12:11 0.49 Ci 0.26 95 79 12:11 0.97 Outfall3 - I - - 12:11 0.97 30 Year Recurrence Interval Event Pre -Development Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff (cfs) EXl 2.04 0 79 12:12 8.98 Junction 1 - 12:12 8.98 OSl 2.68 95 79 12:11 14.65 OS2 1.62 100 79 12:11 8.96 Outfalll - - 12:11 32.59 EX2 0.32 0 79 12:12 1.4 2utfall2 - - 12:12 1.4 EX3 0.57 0 79 12:12 2.5 Outfall3 - - - 12: 12 2.5 Post -Development Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff (cfs) Al 0.45 95 79 12:11 2.49 A2 1.40 95 79 12:11 9.31 A3 0.02 95 79 12:11 0.11 A4 0.17 95 79 12:11 0.94 AS 0.03 95 79 12:11 0.17 A6 0.10 1 95 79 1 12:11 0.55 A7 0.11 95 79 12:11 0.61 A8 0.10 95 79 12:11 0.55 A9 0.02 95 79 12:11 0.11 OSl 2.68 95 79 12:11 14.65 052 1.62 95 79 12:11 8.96 Junction la - - 12:15 4.58 Junction 1 - - 12:13 5.95 Outfall i - 95 79 12:11 29.5 Bl 0.08 95 79 12: 11 0.44 62 0.20 95 79 12:11 0.28 Outfall2 - 1211 0.72 Cl 0.26 95 79 12:11 1.44 Outfall3 - - - 12:11 1.44 25 Year Recurrence Interval Event Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff (cfs) EX1 2.04 0 79 12:11 10.68 Junction 1 - - - 12:11 10.68 051 2.68 95 79 12:11 16.8 052 1.62 100 79 12:11 10.24 OutfallI - - 12:11 37.71 EX2 0.32 0 79 12:11 1.67 Outfall2 - 12:12 1.67 EX3 0.57 1 0 1 79 1 12:11 1 2.97 Outfall3 - I - I - 1 12:12 1 2.97 Post -Development Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff (cfs) At 0.45 95 79 12: 11 2.85 A2 1.40 95 79 12:11 10.65 A3 0.02 95 79 12:11 0.13 A4 0.17 95 79 12:11 1.07 AS 0.03 95 79 12:11 0.19 A6 0.10 95 79 1 12:11 0.63 A7 0.11 95 79 12:11 0.7 AS 0.10 95 79 12:11 0.63 A9 0.02 95 79 12:11 0.13 OSl 2.68 95 79 12:11 16.8 052 1.62 95 79 12:11 10.24 Junction la 12:27 7.43 Junction 1 - - 1226 8.29 Outfall1 95 79 12:11 33.56 B3 0.08 95 79 1 12:11 0.51 B2 0.20 95 79 12:11 0.32 Outfall2 - - 12:11 0.82 C1 0.26 95 79 12:11 1.65 Outfall3 - - - 12:11 1.65 100 Year Recurrence Interval Event Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff (cfs) EXl 2.04 0 79 12:11 13.69 Junction 1 - - - 12:11 13.69 O51 2.68 95 79 12:11 20.23 052 1.62 100 79 12: 11 12.26 Outfall1 - - - 12:11 46.18 EX2 0.32 0 79 12:11 2.14 Outfall2 - - 12.:11 2.14 EX3 0.57 1 0 79 12:11 3.81 Outfall3 - I - - 12:12 1 3.81 Post -Development Results Drainage Area Basin Area (acres) Percent Impervious CN Time to Peak (hh:mn) Max. Runoff Ids) Al 0.45 95 79 12:11 3.42 A2 1.40 95 79 12:11 12.79 A3 0.02 95 79 12:11 0.15 A4 0.17 95 79 12:11 1.29 A5 0.03 95 79 12:11 0.23 A6 1 0.10 95 1 79 12:11 1 0.76 A7 0.11 95 79 12:11 0.84 A8 0.10 95 79 12:11 0.76 A9 0.02 95 79 12:11 0.15 O51 2.68 95 79 12:11 20.23 052 1.62 95 79 12:11 12.26 Junction la 12:22 12.21 Junction 1 - - 12:21 13.59 Outfalll 95 79 12:15 40.7 83 0.08 95 1 79 1 12:11 0.61 82 0.20 95 79 12:11 0.38 Outfall2 - - 12:11 - 0.99 Cl 0.26 95 79 12:11 1.98 Outfall3 - - - 12:11 1.98 Appendix C The Stack at Legacy Point — Storm Sewer LaVout i GS I os ry n o..�< .. _... GS o N-n> i AAo Iv p5 np RA=_ -.- 0853 ,49'99I - M-94,£O.94 N J N GS e 2]�3fi 3] GS z91 I I t— � __�— AO 3Y"7ry 8 4g 4 M$m y a t a�8o z mY- 1nbA�n ➢ON0>n nn A2 A,nA7NAO yT2tA,nm gv,s y mgcr;a oio C n i icmoAmy O z mmo a A`Ocmy^a'm' IN ooY y �go„nn� 7'zY;ggg;m aS�Rm m GG 0 ED by Im m 0 N 0 O Y DE ^^ THE STACK n = RAMPARTS LOT 1-R m CITY OF COLLEGE STATION, TEXAS STORM PLAN <=—__T__�_______ v'Eg>m >_ Asa e m "aA 06U298006 SEA' AS DEIRIMS BY DRAWN BY CRECHES SY £69 - 3.9I,94.La 9 COL>>EPBER. FAMILY, LP TRACT 1- 4.963 ACRES 4073/34 E C]—" Kimley-Horn and Associates, Inc. © 2012 KIIMLEY_40RN AND ASSOCIATES. INC. TYAS REGISTERED ENCwEERING RRM i-S25 $900 SCUTT TEXAS AVENUE, SUITE 20T BRYAN. TR 7780E PHONE979-775-9595 EAR '.c 79-775-9599 I r m m m z 0 REVISIONS I DATE i Cf nag niy �� 7 07 .fir moAkm�g- =Ksm�m.,ma a G1 y m o zi�mgoAmy O o y m * 51�g�mga�y G v V, 492 - OUT p f az , O6<295906 6 � THE STACK GATE �_®rl Kimley-Horn n ozn5izo,z �� a and Associates, Inc. RAMPARTS LOT 1-R STORM CALCULATIONS As showN g a j3 § „.M EY HORN N mA DRAWN BY KHA NDssN 8OX.s R=c SERED ENCEZRNc t ! 92CITY OF COLLEGE STATION, TEXAS 'SDS007H wA5 AYNCE SD3D+ BRYAry 111Kx CHECMED 3Y NJM ` ?HONE'. 919- 9]9->)5-3599 WWW]]5-9595 NIMLE Y-N 04 N.CCM NO. REVISIONS OA7 IBY SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY The Cities of Bryan and College Station both require storm drainage design to follow these Unified Stormwater Design Guidelines. Paragraph C2 of Section III (Administration) requires submittal of a drainage report in support of the drainage plan (stormwater management plan) proposed in connection with land development projects, both site projects and subdivisions. That report may be submitted as a traditional prose report, complete with applicable maps, graphs, tables and drawings, or it may take the form of a "Technical Design Summary". The format and content for such a summary report shall be in substantial conformance with the description in this Appendix to those Guidelines. In either format the report must answer the questions (affirmative or negative) and provide, at minimum, the information prescribed in the "Technical Design Summary" in this Appendix. The Stormwater Management Technical Design Summary Report shall include several parts as listed below. The information called for in each part must be provided as applicable. In addition to the requirements for the Executive Summary, this Appendix includes several pages detailing the requirements for a Technical Design Summary Report as forms to be completed. These are provided so that they may be copied and completed or scanned and digitized. In addition, electronic versions of the report forms may be obtained from the City. Requirements for the means (medium) of submittal are the same as for a conventional report as detailed in Section III of these Guidelines. Note: Part 1 — Executive Summary must accompany any drainage report required to be provided in connection with any land development project, regardless of the format chosen for said report. Note: Parts 2 through 6 are to be provided via the forms provided in this Appendix. Brief statements should be included in the forms as requested, but additional information should be attached as necessary. Part 1 — Executive Summary Report Part 2 — Project Administration Part 3 — Project Characteristics Part 4 — Drainage Concept and Design Parameters Part 5 — Plans and Specifications Part 6 — Conclusions and Attestation SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY STORMWATER MANAGEMENT TECHNICAL DESIGN SUMMARY REPORT Part 1 — Executive Summary This is to be a brief prose report that must address each of the seven areas listed below. Ideally it will include one or more paragraphs about each item. 1 Name, address, and contact information of the engineer submitting the report, and of the land owner and developer (or applicant if not the owner or developer). The date of submittal should also be included. 2 Identification of the size and general nature of the proposed project, including any proposed project phases. This paragraph should also include reference to applications that are in process with either City: plat(s), site plans, zoning requests, or clearing/grading permits, as well as reference to any application numbers or codes assigned by the City to such request. 3 The location of the project should be described. This should identify the Named Regulatory Watershed(s) in which it is located, how the entire project area is situated therein, whether the property straddles a watershed or basin divide, the approximate acreage in each basin, and whether its position in the Watershed dictates use of detention design. The approximate proportion of the property in the city limits and within the ETJ is to be identified, including whether the property straddles city jurisdictional lines. If any portion of the property is in floodplains as described in Flood Insurance Rate Maps published by FEMA that should be disclosed. 4 The hydrologic characteristics of the property are to be described in broad terms: existing land cover; how and where stormwater drains to and from neighboring properties; ponds or wetland areas that tend to detain or store stormwater; existing creeks, channels, and swales crossing or serving the property; all existing drainage easements (or ROW) on the property, or on neighboring properties if they service runoff to or from the property. 5 The general plan for managing stormwater in the entire project area must be outlined to include the approximate size, and extent of use, of any of the following features: storm drains coupled with streets; detention / retention facilities; buried conveyance conduit independent of streets; swales or channels; bridges or culverts; outfalls to principal watercourses or their tributaries; and treatment(s) of existing watercourses. Also, any plans for reclaiming land within floodplain areas must be outlined. 6 Coordination and permitting of stormwater matters must be addressed. This is to include any specialized coordination that has occurred or is planned with other entities (local, state, or federal). This may include agencies such as Brazos County government, the Brazos River Authority, the Texas A&M University System, the Texas Department of Transportation, the Texas Commission for Environmental Quality, the US Army Corps of Engineers, the US Environmental Protection Agency, et al. Mention must be made of any permits, agreements, or understandings that pertain to the project. 7 Reference is to be made to the full drainage report (or the Technical Design Summary Report) which the executive summary represents. The principal elements of the main report (and its length), including any maps, drawings or construction documents, should be itemized. An example statement might be: "One = page drainage report dated one set of construction drawings ( sheets) dated and a -page specifications document dated comprise the drainage report for this project." STORMWATER DESIGN GUIDELINES Page 2 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 AS Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 2 — Project Administration Start (Page 2.1) Engineering and Design Professionals Information Engineering Firm Name and Address: Jurisdiction City: Bryan Kimley-Horn and Associates, Inc. X College Station 2800 South Texas Avenue, Suite 201 Date of Submittal: February 15, Bryan, Texas 77802 2012 Lead Engineer's Name and Contact Info.(phone, e-mail, fax): Other: Chris Harris, P.E. (979) 775-9595 Chris. Harris@kimley-horn.com Supporting Engineering / Consulting Firm(s): Other contacts: Developer / Owner / Applicant Information Developer / Applicant Name and Address: Phone and e-mail: Jack Culpepper 1700 George Bush Drive East, Suite 240 Contact: 979-696-1444 College Station, TX 77840 Property Owner(s) if not Developer / Applicant (& address): Phone and e-mail: Project Identification Development Name: The Stack at Legacy Point Is subject property a site project, a single-phase subdivision, or part of a multi -phase subdivision? Single Phase Pro'ect Improvements If multi -phase, subject property is phase of Legal description of subject property (phase) or Project Area: (see Section II, Paragraph B-3a) Lot 1-R, The Ramparts Subdivision If subject property (phase) is second or later phase of a project, describe general status of all earlier phases. For most recent earlier phase Include submittal and review dates. General Location of Project Area, or subject property (phase): 711 Church Avenue In City Limits? Yes Extraterritorial Jurisdiction (acreage): Bryan: acres. Bryan: College Station: 3.05 acres. College Station: Acreage Outside ETJ: STORMWATER DESIGN GUIDELINES Page 3 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 2 — Project Administration Continued (page 2.2) Project Identification (continued) Roadways abutting or within Project Area or Abutting tracts, platted land, or built `subject property: developments: 1. Culpepper Family, LP, Tract 1 4.983 Acres Church Avenue 2. Culpepper Family, LP, Tract 14.924 Acres 3. John C Culpepper, 1905 Sq. feet 4. Lot 2-R The Ramparts 5. Tract 8, The Ramparts Named Regulatory Watercourse(s) & Watershed(s): Tributary Basin(s): Wolf Pen Creek Plat Information For Project or Subject Property (or Phase) Preliminary Plat File #: Not Applicable Final Plat File #: Not Applicable Date: Name: Status and Vol/P : 4512 / 277 If two plats, second name: File #: Status: Date: Zoning Information For Project or Subject Property (or Phase) Zoning Type: NG-2 Existing or Proposed? Existing Case Code: Not Applicable Case Date Not Applicable Status: Not Applicable Zoning Type: Existing or Proposed? Case Code: Case Date _ Status: Stormwater Management Planning For Project or Subject Property (or Phase) Planning Conference(s) & Date(s): Participants: December 22, 2011 City of College Station, Texas Kimley-Horn and Associates, Inc. 5G Studio Collaborative Collegiate Development Preliminary Report Required? No Submittal Date Review Date Review Comments Addressed? Yes No In Writing? When? Compliance With Preliminary Drainage Report. Briefly describe (or attach documentation explaining) any deviation(s) from provisions of Preliminary Drainage Report, if any. Not Applicable. STORMWATER DESIGN GUIDELINES Page 4 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 2 — Project Administration Continued (page 2.3) Coordination For Project or Subject Property (or Phase) Note: For any Coordination of stormwater matters indicated below, attach documentation describing and substantiating any agreements, understandings, contracts, or approvals. Coordination Dept. Contact: Date: Subject: With Other N/A N/A N/A N/A Departments of Jurisdiction City (Bryan or College Station) Coordination With Summarize need(s) & actions taken (include contacts & dates): Non -jurisdiction City Needed? Yes No X Coordination with Summarize need(s) & actions taken (include contacts & dates): Brazos County Needed? Yes _ No Summarize need(s) & actions taken (include contacts & dates): Coordination with TxDOT Needed? Yes No Summarize need(s) & actions taken (include contacts & dates): Coordination with TAMUS Needed? Yes No X Permits For Project or Subject Property (or Phase) As to stormwater management, are permits required for the proposed work from any of the entities listed below? If so, summarize status of efforts toward that objective in spaces below. Entity Permitted or Approved. Status of Actions (include dates) US Army Corps of Engineers Not Applicable No X Yes US Environmental Protection Agency Not Applicable No X Yes Texas Commission on Environmental Quality Not Applicable Site less than 5ac. NOI not required No _X_ Yes Brazos River Authority Not Applicable No X Yes STORMWATER DESIGN GUIDELINES Page 5 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D — TECHNICAL DESIGN SUMMARY Part 3 — Property Characteristics Start (page 3.1) Nature and Scope of Proposed Work Existing: Land proposed for development currently used, including extent of impervious cover? The existing roadway surface is to be reconstructed. Site Redevelopment of one platted lot, or two or more adjoining platted lots. Development x Building on a single platted lot of undeveloped land. Project Building on two or more platted adjoining lots of undeveloped land. (select all Building on a single lot, or adjoining lots, where proposed plat will not form applicable) a new street (but may include ROW dedication to existing streets). Other (explain): Subdivision Construction of streets and utilities to serve one or more platted lots. Development Construction of streets and utilities to serve one or more proposed lots on Project lands represented by pending plats. Site projects: building use(s), approximate floor space, impervious cover ratio. Describe Subdivisions: number of lots by general type of use, linear feet of streets and Nature and drainage easements or ROW. Size of Proposed 1- 322,359 gsf dormitory residential building. 95% impervious cover Project Is any work planned on land that is not platted If yes, explain: off site storm sewer easement / or on land for which platting is not pending? outfall pipe crosses an unplatted tract No _x_ Yes FEMA Floodplains Is any part of subject property abutting a Named Regulatory Watercourse (Section ll, Paragraph B1) or a tributary thereof? No X Yes Is any part of subject property in floodplain area of a FEMA-regulated watercourse? No _X_ Yes Rate Map Encroachment(s) Encroachment purpose(s): Building site(s) Road crossing(s) into Floodplain Utility crossing(s) Other (explain): areas planned? No X Yes If floodplain areas not shown on Rate Maps, has work been done toward amending the FEMA- approved Flood Study to define allowable encroachments in proposed areas? Explain. STORMWATER DESIGN GUIDELINES Page 6 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 3 — Property Characteristics Continued (Page 3.2) Hydrologic Attributes of Subject Property (or Phase) Has an earlier hydrologic analysis been done for larger area including subject property? Reference the study (& date) here, and attach copy if not already in City files. Yes Is the stormwater management plan for the property in substantial conformance with the earlier study? Yes No If not, explain how it differs. If subject property is not part of multi -phase project, describe stormwater management No plan for the property in Part 4. X If property is part of multi -phase project, provide overview of stormwater management plan for Project Area here. In Part 4 describe how plan for subject property will comply therewith. Do existing topographic features on subject property store or detain runoff? X No Yes Describe them (include approximate size, volume, outfall, model, etc). Any known drainage or flooding problems in areas near subject property? X No Yes Identify: Based on location of study property in a watershed, is Type 1 Detention (flood control) needed? (see Table B-1 in Appendix B) x Detention is required. Need must be evaluated. Detention not required. What decision has been reached? By whom? If the need for Type 1 Detention must How was determination made? be evaluated: STORMWATER DESIGN GUIDELINES Page 7 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 3 — Property Characteristics Continued (Page 3.3) Hydrologic Attributes of Subject Property (or Phase) (continued) Does subject property straddle a Watershed or Basin divide? X No Yes If yes, describe splits below. In Part 4 describe design concept for handling this. Watershed or Basin Larger acreage Lesser acreage Above -Project Areas(Section II, Paragraph B3-a) Does Project Area (project or phase) receive runoff from upland areas? x No _ Yes Size(s) of area(s)in acres:1) 2) 3) 4) Flow Characteristics (each instance) (overland sheet, shallow concentrated, recognizable concentrated section(s), small creek (non -regulatory), regulatory Watercourse or tributary); Flow determination: Outline hydrologic methods and assumptions: Does storm runoff drain from public easements or ROW onto or across subject property? X—No Yes If yes, describe facilities in easement or ROW: Are changes in runoff characteristics subject to change in future? Explain Conveyance Pathways (Section II, Paragraph C2) Must runoff from study property drain across lower properties before reaching a Regulatory Watercourse or tributary? No X Yes Describe length and characteristics of each conveyance pathway(s). Include ownership of property(ies). The property currently discharges onto 3 properties. The northern portion discharges onto the adjacent drive aisle for Tract B of The Ramparts. The eastern portion discharges onto the drive aisle behind the retail development owned by the Culpeper Family L.P. The southern portion discharges onto property owned by the Culpepper Family L.P. All discharge paths are developed property with paved drainage ways. STORMWATER DESIGN GUIDELINES Page 8 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 3 — Property Characteristics Continued (Page 3.4) Hydrologic Attributes of Subject Property (or Phase) (continued) Conveyance Pathways (continued) Do drainage If yes, for what part of length? % Created by? plat, or easements _instrument. If instrument(s), describe their provisions. exist for any part of pathway(s)? X No Yes Where runoff must cross lower properties, describe characteristics of abutting lower property(ies). (Existing watercourses? Easement or Consent required?) Lower properties are currently developed. Water discharges into existing paved Pathway parking and drive aisle areas. Areas Describe any built or improved drainage facilities existing near the property (culverts, bridges, lined channels, buried conduit, swales, detention ponds, etc). An existing curb inlet north of Taco Bell, east of Church Avenue is the receiving structure for the majority of discharge from the site and the surrounding areas. This inlet connects south to the existing TxDOT storm system. Areas discharging north and east travel north to an existing Swale along the northern property line of the Culpepper Family property which discharges to the South College Right of Way. Nearby Drainage Do any of these have hydrologic or hydraulic influence on proposed stormwater Facilities design? X No Yes If yes, explain: STORMWATER DESIGN GUIDELINES Page 9 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Start (Page 4.1) Stormwater Management Concept Discharge(s) From Upland Area(s) If runoff is to be received from upland areas, what design drainage features will be used to accommodate it and insure it is not blocked by future development? Describe for each area, flow section, or discharge point. Discharge(s) To Lower Property(ies) (Section II, Paragraph El) Does project include drainage features (existing or future) proposed to become public via platting? X No Yes Separate Instrument? X No Yes Per Guidelines reference above, how will runoff Establishing Easements (Scenario 1) be discharged to neighboring property(ies)? Pre -development Release (Scenario 2) x Combination of the two Scenarios Scenario 1: If easements are proposed, describe where needed, and provide status of actions on each. (Attached Exhibit # ) A single drainage easement is needed for the connection of the storm sewer pipe outfall from the property south to the existing inlet box. This easement is proposed to be a 15' drainage easement by separate instrument. The easement is not currently filed. Scenario 2: Provide general description of how release(s) will be managed to pre -development conditions (detention, sheet flow, partially concentrated, etc.). (Attached Exhibit # Appendix C1 & C2) Releases onto adjacent property will be mitigated via limiting proposed drainage areas and through detention. Combination: If combination is proposed, explain how discharge will differ from pre - development conditions at the property line for each area (or point) of release. Discharges will not differ at the property line. Easement is needed for connection of proposed underground system to the existing underground system. If Scenario 2, or Combination are to be used, has proposed design been coordinated with owner(s) of receiving property(ies)? No _X Yes Explain and provide documentation. The owner of the receiving property requiring and easement is the same owner as the developer. STORMWATER DESIGN GUIDELINES Page 10 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D -TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.2) Stormwater Management Concept (continued) Within Project Area Of Multi -Phase Project Identify gaining Basins or Watersheds and acres shifting: Will project result in shifting runoff between Basins or between What design and mitigation is used to compensate for increased runoff from Watersheds? gaining basin or watershed? X No Yes How will runoff from Project 1. With facility(ies) involving other development projects. Area be mitigated to pre- 2. Establishing features to serve overall Project Area. development conditions? 3. On phase (or site) project basis within Project Area. Select any or all of 1, 2, and/or 3, and explain below. Not Applicable. 1. Shared facility (type & location of facility; design drainage area served; relationship to size of Project Area): (Attached Exhibit # ) 2. For Overall Project Area (type & location of facilities): (Attached Exhibit # ) 3. By phase (or site) project: Describe planned mitigation measures for phases (or sites) in subsequent questions of this Part. Are aquatic ecosystems proposed? X No Yes In which phase(s) or project(s)? Are other Best Management Practices for reducing stormwater pollutants proposed? } X No Yes Summarize type of BMP and extent of use: (I> z° x If design of any runoff -handling facilities deviate from provisions of B-CS Technical n Specifications, check type facility(ies) and explain in later questions. to Detention elements Conduit elements Channel features a) Swales Ditches Inlets Valley gutters Outfalls Culvert features Bridges Other STORMWATER DESIGN GUIDELINES Page 11 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 AS Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.3) Stormwater Management Concept (continued) Within Project Area Of Multi -Phase Project (continued) Will Project Area include bridge(s) or culvert(s)? No —_ Yes Identify type and general size and In which phase(s). Not Applicable. If detention/retention serves (will serve) overall Project Area, describe how it relates to subject phase or site project (physical location, conveyance pathway(s), construction sequence): Not Applicable. Within Or Serving Subject Property (Phase, or Site) If property part of larger Project Area, is design in substantial conformance with earlier analysis and report for larger area? Yes No, then summarize the difference(s): Identify whether each of the types of drainage features listed below are included, extent of use, and general characteristics. Typical shape? Surfaces? o Steepest side slopes: Usual front slopes: Usual back slopes: Y Flow line slopes: least Typical distance from travelway: 0o z typical greatest (Attached Exhibit # ) v, m x ° Are longitudinal culvert ends in compliance with B-CS Standard Specifications? Yes No, then explain: N At intersections or otherwise, do valley gutters cross arterial or collector streets? D — No Yes If yes explain: L � 3 � A 2 Are valley gutters proposed to cross any street away from an intersection? MZ No —Yes Explain: (number of locations?) '65 -0 X STORMWATER DESIGN GUIDELINES Page 12 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.4) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Gutter line slopes: Least Usual Greatest Are inlets recessed on arterial and collector streets? Yes No If "no", identify where and why. Will inlets capture 10-year design stormflow to prevent flooding of intersections (arterial with arterial or collector)? Yes _ No If no, explain where and -moo why not. 2 Will inlet size and placement prevent exceeding allowable water spread for 10-year } design storm throughout site (or phase)? Yes No If no, explain. c m I C Sag curves: Are inlets placed at low points? Yes _ No Are inlets and conduit sized to prevent 100-year stormflow from ponding at greater than 24 3 X� inches? Yes —No Explain "no" answers. � I a� Will 100-yr stormflow be contained in combination of ROW and buried conduit on whole length of all streets? Yes No If no, describe where and why. Do designs for curb, gutter, and inlets comply with B-CS Technical Specifications? Yes No If not, describe differences) and attach justification. Are any 12-inch laterals used? X No Yes Identify length(s) and where used. Pipe runs between system access Typical 75 ft Longest 156 ft E points (feet): ax T Are junction boxes used at each bend? X Yes No If not, explain where and why. c m o Z E Are downstream soffits at or below upstream soffits? Least amount that Yes X No If not, explain where and why: hydraulic grade line is N below gutter line (system- wide): 1.66' STORMWATER DESIGN GUIDELINES Page 13 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.5) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Describe watercourse(s), or system(s) receiving system discharge(s) below (include design discharge velocity, and angle between converging flow lines). 1) Watercourse (or system), velocity, and angle? Southern outfall receives water via 24" rcp pipe junctioned to an existing inlet at 90 degrees, max velocity 4. lips 2) Watercourse (or system), velocity, and angle? m O 3) Watercourse (or system), velocity, and angle? `o ° For each outfall above, what measures are taken to prevent erosion or scour of c o receiving and all facilities at juncture? m All outfalls are either paved or existing storm drain conduits. m o a Are swale(s) situated along property lines between properties? No Yes m Number of instances: 1 For each instance answer the following questions. N Surface treatments (including low -flow flumes if any): 0 m o � � o O Flow line slopes (minimum and maximum): o� -`o 0 0 0 z Outfall characteristics for each (velocity, convergent angle, & end treatment). a) o 3 xl a� < Will 100-year design storm runoff be contained within easement(s) or platted drainage ROW in all instances? Yes No If "no" explain: STORMWATER DESIGN GUIDELINES Page 14 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D -TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.6) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Are roadside ditches used? No Yes If so, provide the following: a) Is 25-year flow contained with 6 inches of freeboard throughout ? Yes No Are top of banks separated from road shoulders 2 feet or more? Yes No _ Are all ditch sections trapezoidal and at least 1.5 feet deep? Yes No For any "no" answers provide location(s) and explain: 0 If conduit is beneath a swale, provide the following information (each instance). N Instance 1 Describe general location, approximate length: x c @ Is 100-year design flow contained in conduit/swale combination? Yes No If N "no" explain: Space for 100-year storm flow? ROW Easement Width @ Swale Surface type, minimum and Conduit Type and size, minimum and o > maximum slopes: maximum slopes, design storm: c � a f6 0 o Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type): O G 2 N E Access Describe how maintenance access is provided (to Swale, into conduit): 0 � ( c N Instance 2 Describe general location, approximate length: c m o v, _ 2 Is 100-year design flow contained in conduit/swale combination? _ Yes _ No If 'o E "no" explain: ° Space for 100-year storm flow? ROW Easement Width mSwale Surface type, minimum and Conduit Type and size, minimum and c maximum slopes: maximum slopes, design storm: 0 o Describe how conduit is loaded (from streets/storm drains, inlets by type): Co m o_ o Access Describe how maintenance access is provided (to swale, into conduit): o � 0 Q STORMWATER DESIGN GUIDELINES Page 15 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.7) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) If "yes" provide the following information for each instance: Instance 1 Describe general location, approximate length, surfacing: Is 100-year design flow contained in swale? Yes No Is swale wholly a _ within drainage ROW? Yes No Explain "no" answers: 0 } Access Describe how maintenance access is provide: 0 Instance 2 Describe general location, approximate length, surfacing: z 3 yX co Is 100-year design flow contained in swale? Yes No Is swale wholly —_ within drainage ROW? Yes No Explain "no" answers: Access Describe how maintenance access is provided: Instance 3, 4, etc. If swales are used in more than two instances, attach sheet providing all above information for each instance. "New" channels: Will any area(s) of concentrated flow be channelized (deepened, widened, or straightened) or otherwise altered? No Yes If only slightly shaped, see "Swales" in this Part. If creating side banks, provide information below. a) Will design replicate natural channel? _Yes No If "no", for each instance o fl describe section shape & area, flow line slope (min. & max.), surfaces, and 100-year o Lu design flow, and amount of freeboard: a j Instance 1: E 0 ° Instance 2: a E 0 —z X Instance 3: m U STORMWATER DESIGN GUIDELINES Page 16 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 AS Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.8) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Existing channels (small creeks): Are these used? No _ Yes If "yes" provide the information below. Will small creeks and their floodplains remain undisturbed? Yes No How _ many disturbance instances? Identify each planned location: For each location, describe length and general type of proposed improvement (including floodplain changes): For each location, describe section shape & area, flow line slope (min. & max.), surfaces; and 100-year design flow. Watercourses (and tributaries): Aside from fringe changes, are Regulatory 5 Watercourses proposed to be altered? X No Yes Explain below. c ° Submit full report describing proposed changes to Regulatory Watercourses. Address existing and proposed section size and shape, surfaces, alignment, flow line changes, length affected, and capacity, and provide full documentation of E analysis procedures and data. Is full report submitted? Yes No o If "no" explain: E a� C C m �j All Proposed Channel Work: For all proposed channel work, provide information requested in next three boxes. If design is to replicate natural channel, identify location and length here, and describe design in Special Design section of this Part of Report. Will 100-year flow be contained with one foot of freeboard? Yes No If not, identify location and explain: Are ROW / easements sized to contain channel and required maintenance space? Yes No If not, identify location(s) and explain: STORMWATER DESIGN GUIDELINES Page 17 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.9) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) How many facilities for subject property project? 1 For each provide info. below. Not Applicable For each dry -type facility: Facility 1 Facility 2 Acres served & design volume + 10% 2.4 0.41 ac-ft 100-yr volume: free flow & plugged 0.37 0.43 ac-ft Design discharge (10 yr & 25 yr) 3.92 6.58 Spillway crest at 100-yr WSE? _yes x no _yes _no Berms 6 inches above plugged WSE? _Yes _x_ no yes no Explain any "no" answers: System is an underground detention system. A weir inside a 4'x4' junction box controls the 100-year flow. A emergency outfall in the form of a grate top is designed on the junction box. Emergency spillway is 1.66' above plugged WSE: For each facility what is 25-yr design Q, and design of outlet structure? a Facility 1: Q25 =6.58 cfs design discharge. 0 Outlet is a 6"x10" wide orifice and a 4' wide weir. n 0 0 z 2- Facility 2: Do outlets and spillways discharge into a public facility in easement or ROW? Facility 1: Yes X No Facility 2: —Yes—No If "no" explain: UL >- The detention pond outfalls into a storm system that ties directly into an existing s storm system on the adjacent property x� I For each, what is velocity of 25-yr design discharge at outlet? & at spillway? o at Facility 1: 8.88 & 1.77 Facility 2: & Q Are energy dissipation measures used? x No Yes Describe type and location: For each, is spillway surface treatment other than concrete? Yes r no, and describe: Facility 1: For each, what measures are taken to prevent erosion or scour at receiving facility? Facility 1: discharge into storm system Facility 2: If berms are used give heights, slopes and surface treatments of sides. Facility 1: Facility 2: STORMWATER DESIGN GUIDELINES Page 18 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.10) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Do structures comply with B-CS Specifications? Yes or _no, and explain if _x "no": Not Applicable Facility 1: c 4 c = o Facility 2: o .m m For additional facilities provide all same information on a separate sheet. LL Are parking areas to be used for detention? _x_ No Yes What is maximum depth due to required design storm? Roadside Ditches: Will culverts serve access driveways at roadside ditches? _ No _ Yes If "yes", provide information in next two boxes. Will 25-yr. flow pass without flowing over driveway in all cases? Yes No Without causing flowing or standing water on public roadway? Yes No Designs & materials comply with B-CS Technical Specifications? Yes No Explain any "no" answers: r, m m c oAre culverts parallel to public roadway alignment? No Explain: —Yes U U N N >_ Q Creeks at Private Drives: Do private driveways, drives, or streets cross drainage o ways that serve Above -Project areas or are in public easements/ ROW? No z Yes If "yes" provide information below. xI How many instances? Describe location and provide information below. y Location 1: a� U E Location 2: Location 3: For each location enter value for: 1 2 3 Design year passing without toping travelway? Water depth on travelway at 25-year flow? Water depth on travelway at 100-year flow? For more instances describe location and same information on separate sheet. STORMWATER DESIGN GUIDELINES Page 19 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 AS Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.11) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Named Regulatory Watercourses (& Tributaries): Are culverts proposed on these facilities? No Yes, then provide full report documenting assumptions, criteria, analysis, computer programs, and study findings that support proposed design(s). Is report provided? Yes No If "no", explain: Arterial or Major Collector Streets: Will culverts serve these types of roadways? No Yes How many instances? For each identify the location and e information below. the Instance 1: Instance 2: Instance 3: Yes or No for the 100-year design flow: 1 2 3 Headwater WSE 1 foot below lowest curb top? Spread of headwater within ROW or easement? 0 Is velocity limited per conditions (Table C-11)? Explain any "no" answer(s): o. m M Minor Collector or Local Streets: Will culverts serve these types of streets? No Yes How many instances? for each identify the location > and provide the information below: Instance 1: S Instance 2: Instance 3: For each instance enter value, or "yes" / "no" for: 1 2 3 Design yr. headwater WSE 1 ft. below curb top? 100-yr. max. depth at street crown 2 feet or less? Product of velocity (fps) & depth at crown (ft) = ? Is velocity limited per conditions (Table C-11)? Limit of downstream analysis (feet)? Explain any "no" answers: STORMWATER DESIGN GUIDELINES Page 20 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 AS Revised February 2008 SECTION IX G" ►� .► ► 1111T: 1 Part 4 — Drainage Concept and Design Parameters Continued (Page 4.12) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) All Proposed Culverts: For all proposed culvert facilities (except driveway/roadside ditch intersects) provide information requested in next eight boxes. Do culverts and travelways intersect at 90 degrees? Yes _ No If not, identify location(s) and intersect angle(s), and justify the design(s): Does drainage way alignment change within or near limits of culvert and surfaced approaches thereto? No Yes If "yes" identify location(s), describe change(s), and justification: Are flumes or conduit to discharge into culvert barrel(s)? No Yes If yes, identify location(s) and provide justification: Are flumes or conduit to discharge into or near surfaced approaches to culvert ends? No Yes If "yes" identify location(s), describe outfall design treatment(s): ma > Y c U 2 U Is scour/erosion protection provided to ensure long term stability of culvert structural components, and surfacing at culvert ends? Yes _ No If "no" Identify locations and provide justification(s): 1. 2. Will 100-yr flow and spread of backwater be fully contained in street ROW, and/or I drainage easements/ ROW? —Yes No if not, why not? It is not currently contained in street or ROW. Do appreciable hydraulic effects of any culvert extend downstream or upstream to neighboring land(s) not encompassed in subject property? No Yes If "yes" describe location(s) and mitigation measures: Are all culvert designs and materials in compliance with B-CS Tech. Specifications? Yes No If not, explain in Special Design Section of this Part. STORMWATER DESIGN GUIDELINES Page 21 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 - As Revised February 2008 SECTION IX Part 4 — Drainage Concept and Design Parameters Continued (Page 4.13) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Is a bridge included in plans for subject property project? X No Yes If "yes' provide the following information. Name(s) and functional classification of the roadway(s)? What drainage way(s) is to be crossed? a m m` A full report supporting all aspects of the proposed bridge(s) (structural, geotechnical, hydrologic, and hydraulic factors) must accompany this summary report. Is the report provided? Yes _ No If "no" explain: Is a Stormwater Provide a general description of planned techniques: w Pollution Prevention Plan (SW3P) Storm water pollution control measures during construction 0 established for will include silt fence, inlet protection, construction entrances, project construction? and other best management practices as required. No X Yes Special Designs — Non -Traditional Methods Are any non-traditional methods (aquatic ecosystems, wetland -type detention, natural stream replication, BMPs for water quality, etc.) proposed for any aspect of subject property project? X No Yes If "yes" list general type and location below. Provide full report about the proposed special design(s) including rationale for use and expected benefits. Report must substantiate that stormwater management objectives will not be compromised, and that maintenance cost will not exceed those of traditional design solution(s). Is report provided? Yes No If "no" explain: Not Applicable. STORMWATER DESIGN GUIDELINES Page 22 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D - TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.14) Stormwater Management Concept (continued) Within Or Serving Subject Property (Phase, or Site) (continued) Special Designs — Deviation From B-CS Technical Specifications If any design(s) or material(s) of traditional runoff -handling facilities deviate from provisions of B-CS Technical Specifications, check type facility(ies) and explain by specific detail element. Detention elements Drain system elements Channel features Culvert features Swales Ditches Inlets Outfalls Valley gutters Bridges (explain in bridge report) In table below briefly identify specific element, justification for deviation(s). Specific Detail Element Justification for Deviation (attach additional sheets if needed) 1) 2) 3) 4) 5) Have elements been coordinated with the City Engineer or her/his designee? For each item above provide "yes' or "no", action date, and staff name: 1) 2) 3) 4) 5) Design Parameters Hydrology Is a map(s) showing all Design Drainage Areas provided? X Yes No Briefly summarize the range of applications made of the Rational Formula: All flows have been generated using HEC-HMS. No rational method has been applied. What is the size and location of largest Design Drainage Area to which the Rational Formula has been applied? We acres Location (or identifier): STORMWATER DESIGN GUIDELINES Page 23 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D — TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.15) Design Parameters (continued) Hydrology (continued) In making determinations for time of concentration, was segment analysis used? _ No _X_Yes In approximately what percent of Design Drainage Areas? 100 As to intensity -duration -frequency and rain depth criteria for determining runoff flows, were any criteria other than those provided in these Guidelines used? X No _Yes If "yes" identify type of data, source(s), and where applied: For each of the stormwater management features listed below identify the storm return frequencies (year) analyzed (or checked), and that used as the basis for design. Feature Analysis Year(s) Design Year Storm drain system for arterial and collector streets Storm drain system for local streets Open channels Swale/buried conduit combination in lieu of channel Swales Roadside ditches and culverts serving them Detention facilities: spillway crest and its outfall 2, 10, 25, 100 100 Detention facilities: outlet and conveyance structure(s) 2, 10, 25, 100 100 Detention facilities: volume when outlet plugged 100 100 Culverts serving private drives or streets Culverts serving public roadways Bridges: provide in bridge report. Hydraulics What is the range of design flow velocities as outlined below? Design flow velocities; Gutters Conduit Culverts Swales Channels Highest (feet per second) 4.10 fps Lowest (feet per second) 0.57 fps Streets and Storm Drain Systems Provide the summary information outlined below: Roughness coefficients used: For street gutters: For conduit type(s) RCP Coefficients: 0.013 0.017 STORMWATER DESIGN GUIDELINES Page 24 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D — TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.16) Design Parameters (continued) Hydraulics (continued) Street and Storm Drain Systems (continued) For the following, are assumptions other than allowable per Guidelines? Inlet coefficients? X No Yes Head and friction losses X No Yes Explain any "yes" answer: In conduit is velocity generally increased in the downstream direction? X Yes No Are elevation drops provided at inlets, manholes, and junction boxes? X Yes No Explain any "no" answers: Are hydraulic grade lines calculated and shown for design storm? X Yes No For 100-year flow conditions? X Yes No Explain any "no" answers: What tailwater conditions were assumed at outfall point(s) of the storm drain system? Identify each location and explain: At the outfall junction of the existing curb inlet, top of curb was assumed for the tailwater elevation. Open Channels If a HEC analysis is utilized, does it follow Sec VI.F.5.a? Yes No Outside of straight sections, is flow regime within limits of sub -critical flow? Yes No If "no" list locations and explain: Culverts If plan sheets do not provide the following for each culvert, describe it here. For each design discharge, will operation be outlet (barrel) control or inlet control? Entrance, friction and exit losses: Bridges Provide all in bridge report STORMWATER DESIGN GUIDELINES Page 25 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2007 As Revised February 2008 SECTION IX APPENDIX D — TECHNICAL DESIGN SUMMARY Part 4 — Drainage Concept and Design Parameters Continued (Page 4.17) Design Parameters (continued) Computer Software What computer software has been used in the analysis and assessment of stormwater management needs and/or the development of facility designs proposed for subject property project? List them below, being sure to identify the software name and version, the date of the version, any applicable patches and the publisher HEC-HMS; Version 3.5; August 10, 2010; U.S. Army Corps of Engineers Office Excel® 2007; (12.0.6214.1000) SP1 MSO (12.0.6213.1000); ©2006 Microsoft Corporation Part 5 — Plans and Specifications Requirements for submittal of construction drawings and specifications do not differ due to use of a Technical Design Summary Report. See Section III, Paragraph C3. Part 6 — Conclusions and Attestation Conclusions Add any concluding information here: Attestation Provide attestation to the accuracy and completeness of the foregoing 6 Parts of this Technical Design Summary Drainage Report by signing and sealing below. "This report (plan) for the drainage design of the development named in Part B was prepared by me (or under my supervision) in accordance with provisions of the Bryan/College Station Unified Drainage Design Guidelines for the owners of the property. All licenses and permits required by any and all state and federal regulatory agencies for the proposed drainage improvements have been issued or fall under applicable general permits." ... lc `, oz• Z . Licensed Professional Engineer ' 10 {+� :fir 3: CHRtS HARRIS State of Texas PE No. 94859 � STORMWATER DESIGN GUIDELINES Page 26 of 26 APPENDIX D: TECH. DESIGN SUMMARY Effective February 2G07 As Revised February 2008